1. Field of the Invention
The present invention relates to a sheet feeding apparatus and an image forming apparatus, particularly to a configuration of a lateral-end regulating portion which regulates a lateral-end position of a sheet stored in a sheet feeding cassette detachably attached to the sheet feeding apparatus.
2. Description of the Related Art
Nowadays, an image forming apparatus in which a sheet feeding apparatus feeds a sheet to an image forming portion to form an image is widely spread in image forming apparatuses, such as a copying machine, a printer, and a facsimile machine. As to the sheet feeding apparatus, generally a sheet feeding cassette is detachably attached to an apparatus body, and the sheet stored in the sheet feeding cassette is automatically fed to an image forming portion.
For example, in some of the sheet feeding cassettes used in the sheet feeding apparatus, a sheet supporting plate which presses the stacked sheet against a feeding roller is provided while being able to be lifted and lowered. A rear-end regulating portion is slidably provided in the sheet feeding cassette in which the sheet supporting plate is provided. The rear-end regulating portion regulates a position at an end (hereinafter referred to as a rear end) on an upstream side in a sheet feeding direction of the sheet stacked and stored on the sheet supporting plate such that the sheets having different sizes can be stored. A pair of lateral-end regulating portions is also provided in order to regulate a lateral-end position in a direction (hereinafter referred to as a width direction) orthogonal to the sheet feeding direction.
The pair of lateral-end regulating portions regulates lateral ends of the sheet, and the rear-end regulating portion regulates the rear end of the sheet, whereby the sheet is always regulated in a predetermined position. Therefore, when the sheet feeding cassette is accommodated in the apparatus body, the sheet can be fed from the fixed position irrespective of a size of the sheet. In a sheet feeding cassette of the related art, a guide projection is provided in an upper end part of a sheet abutting surface of the lateral-end regulating portion such that an end part of the sheet does not climb over the lateral-end regulating portion when the sheet is fed.
When the sheet is left in a low-temperature, low-humidity environment, the sheet is warped (hereinafter referred to as curled), and both end parts of the sheet rise. As illustrated in FIG. 9A, when a sheet S is curled, a clearance K is generated between the end part of the sheet S and each of projections 42T and 43T, and therefore sometimes the end part of the sheet S climbs over lateral-end regulating portions 42 and 43 when feeding the sheet S.
When the end part of the sheet S climbs over the lateral-end regulating portions 42 and 43, the sheet S generates a skew feeding, or the sheet S is fed while deviated in the width direction. When sheet feeding performance is degraded in this way, possibly print accuracy is degraded, or a jam is generated. Meanwhile, when projection amounts of the projections 42T and 43T are increased in a sheet direction, the sheet S does not climb over the lateral-end regulating portions 42 and 43. However, the sheet S is hardly set, and possibly the projections 42T and 43T damage the end part of the sheet. Therefore, from the viewpoint of usability, it is not preferable that the projection amounts of the projections 42T and 43T be increased.
Conventionally, in order to solve the problem, projections 42k and 43k are rotatably provided in the lateral-end regulating portions 42 and 43 as illustrated in FIG. 9B (see Japanese Patent Laid-Open No. 2007-197184). When the sheet is set in the sheet feeding cassette disclosed in Japanese Patent Laid-Open No. 2007-197184, the projections 42k and 43k are rotated in direction of an arrow C about guide projection centers 42s and 43s, which allows the sheet to be set without degrading the usability.
In the sheet feeding apparatus of the related art, it is necessary that the projections 42k and 43k be returned to climbing-over regulating positions parallel to the sheet after the projections 42k and 43k are rotated in the direction of the arrow C to set the sheet. However, as illustrated in FIG. 9B, in order to return the projections 42k and 43k to the climbing-over regulating positions, a height of the sheet feeding apparatus is increased by a projection amount F of the guide projection, and the number of components is increased to lead to an increase in cost.
Therefore, the invention is aimed at a sheet feeding apparatus and an image forming apparatus, which can improve the sheet feeding performance at low cost without degrading the usability.